In the operation of CCDs, charge trapping during the transfer of the charge along the CCD typically limits charge transfer efficiency. This is particularly true under conditions of low temperatures and high operating speeds. This degrades device performance, especially for low signal levels. Charge trapping can occur at a variety of sites in the CCD. Such sites includes crystallographic imperfections, metallic impurities and ionized donors and acceptors. Although crystallographic imperfections can be limited by process improvements, trapping at donor sites still deteriorates performance. This is due to the necessity of dopants for channel potential control. Surface channel devices have been employed to reduce the problem of trapping at donor sites. However, this still leaves surface state trapping which is difficult to avoid. The use of unconventional dopants with energy levels more shallow than the donors conventionally used, such as boron and phosphorus, allow device operation at lower temperatures, but do not fundamentally solve the problem of impurity trapping.